The units of measurement in transportation describes the
unit of measurement
A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other quantity of that kind can be expressed as a mult ...
used to express various
transportation
Transport (in British English), or transportation (in American English), is the intentional movement of humans, animals, and goods from one location to another. Modes of transport include air, land ( rail and road), water, cable, pipel ...
quantities, as used in statistics, planning, and their related applications.
Transportation quantity
The currently popular units are:
Length of journey
*
kilometre
The kilometre ( SI symbol: km; or ), spelt kilometer in American English, is a unit of length in the International System of Units (SI), equal to one thousand metres ( kilo- being the SI prefix for ). It is now the measurement unit used for ...
(km) or kilometer is a
metric unit used, outside the US, to measure the length of a journey;
* the international
statute mile
The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and United States customary unit of distance; both are based on the older English unit of length equal to 5,280 Engli ...
(mi) is used in the US; 1 mi = 1.609344 km
*
nautical mile
A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. Historically, it was defined as the meridian arc length corresponding to one minute ( of a degree) of latitude. Today t ...
is rarely used to derive units of transportation quantity.
Traffic flow
* vehicle-kilometre (vkm
) as a measure of
traffic flow
In mathematics and transportation engineering, traffic flow is the study of interactions between travellers (including pedestrians, cyclists, drivers, and their vehicles) and infrastructure (including highways, signage, and traffic control de ...
, determined by multiplying the number of vehicles on a given road or traffic network by the average length of their trips measured in kilometres.
* vehicle-mile (, or VMT) same as before but measures the trip expressed in miles.
Passenger
Payload quantity
*
Passenger
A passenger (also abbreviated as pax) is a person who travels in a vehicle, but does not bear any responsibility for the tasks required for that vehicle to arrive at its destination or otherwise operate the vehicle, and is not a steward. The ...
; Person (often abbreviated as either "pax" or "p.")
Passenger-distance
Passenger-distance is the distance (km or miles) travelled by passengers on
transit vehicles; determined by multiplying the number of unlinked passenger trips by the average length of their trips.
* passenger-kilometre or pkm internationally;
* passenger-mile (or pmi ?) sometimes in the US; 1 pmi = 1.609344 pkm
Passengers per hour per direction
Passengers per hour per direction
Passengers per hour per direction (p/h/d), passengers per hour in peak direction (pphpd) or corridor capacity is a measure of the route capacity of a rapid transit or public transport system.
Definition
The corridor capacity in the passenger tr ...
(pphpd) measures the maximum
route capacity of a transport system.
Passengers per bus hour
A system may carry a high number of passengers per distance (km or mile) but a relatively low number of passengers per bus hour if vehicles operate in
congested areas and thus travel at slower speed.
Passengers per bus distance
A transit system serving a community with a widely dispersed population must operate circuitous routes that tend to carry fewer passengers per distance (km or mile). A higher number is more favorable.
Freight
Freight is measured in mass-distance. A simple unit of freight is the kilogram-kilometre (kgkm), the service of moving one kilogram of payload a distance of one kilometre.
Payload quantity
*
kilogram
The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially ...
(kg), the standard
SI unit of mass.
*
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
(t), a non-
SI but an accepted metric unit, defined as 1,000
kilogram
The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially ...
s.
* "
short ton
The short ton (symbol tn) is a measurement unit equal to . It is commonly used in the United States, where it is known simply as a ton,
although the term is ambiguous, the single word being variously used for short, long, and metric ton.
The vari ...
" is used in the US; 1 short ton = 2,000
pounds = 0.907 tonnes.
:1 t = (1/0.907) short tons = 1.102 short tons.
Payload-distance
* kilogram-kilometre (kg⋅km), moving 1 kg of cargo a distance of 1 km;
* tonne-kilometre or kilometre-tonne (t⋅km or km⋅t, also tkm or kmt), the transportation of one
tonne
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...
over one
kilometre
The kilometre ( SI symbol: km; or ), spelt kilometer in American English, is a unit of length in the International System of Units (SI), equal to one thousand metres ( kilo- being the SI prefix for ). It is now the measurement unit used for ...
; 1 tkm = 1,000 kgkm.
* ton-mile in the US: 1 ton-mile * ( 0.907185 t / short ton) * ( 1.609344 km / mile ) = 1.460 tkm
Usage
The
metric units (pkm and tkm) are used internationally.
(In
aviation
Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot ...
where
United States customary units
United States customary units form a system of Units of measurement, measurement units commonly used in the United States and Territories of the United States, U.S. territories since being standardized and adopted in 1832. The United States cust ...
are widely used,
the
International Air Transport Association
The International Air Transport Association (IATA ) is a trade association of the world's airlines founded in 1945. IATA has been described as a cartel since, in addition to setting technical standards for airlines, IATA also organized tar ...
(IATA) releases its statistics in the metric units.)
In the US, sometimes United States customary units are used.
Derivation
The
dimension
In physics and mathematics, the dimension of a mathematical space (or object) is informally defined as the minimum number of coordinates needed to specify any point within it. Thus, a line has a dimension of one (1D) because only one coor ...
of the measure is the product of the payload mass and the distance transported.
Example
A
semi truck traveling from Los Angeles to Chicago (approximate distance 2,015 miles) carrying 14 short tons of cargo delivers a service of 14 * 2,015 = 28,210 ton-miles of freight (equal to about 41,187 tkm).
Intermodal containers
Intermodal container
An intermodal container, often called a shipping container, is a large standardized shipping container, designed and built for intermodal freight transport, meaning these containers can be used across different modes of transport – from sh ...
traffic is commonly measured in
twenty-foot equivalent units (TEUs), rather than cargo weight, e.g. a TEU-km would be the equivalent of one twenty-foot container transported one kilometer.
Transportation density
Transportation density can be defined as the payload per period, say passenger / day or tonne / day. This can be used as the measure of intensity of the transportation on a particular section or point of transportation infrastructure, say road or railway. This can be used in comparison with the construction, running costs of the infrastructure.
Fatalities by VMT
Fatalities by VMT (
vehicle miles traveled) is a unit for assessing road traffic fatalities. This metric is computed by dividing the fatalities by the estimated VMT.
Usually, transport risk is computed by reference to the distance traveled by people, while for road traffic risk, only vehicle traveled distance is usually taken into account.
In the United States, the unit is used as an aggregate in yearly federal publications, while its usage is more sporadic in other countries. For instance, it appears to compare different kind of roads in some publications as it had been computed on a five-year period between 1995 and 2000.
[http://dtrf.setra.fr/pdf/pj/Dtrf/0002/Dtrf-0002649/DT2649.pdf ]
In the United States, it is computed per 100 million miles traveled, while internationally it is computed in 100 million or 1 billion kilometers traveled.
According to the Minnesota Department of Public Safety, Office of Traffic Safety
Energy efficiency
Energy efficiency in transport can be measured in L/100 km or miles per gallon (mpg). This can be normalized per vehicle, as in
fuel economy in automobiles
The fuel economy of an automobile relates distance traveled by a vehicle and the amount of fuel consumed. Consumption can be expressed in terms of volume of fuel to travel a distance, or the distance traveled per unit volume of fuel consumed. S ...
, or per seat, as for example in
fuel economy in aircraft.
History
MacNeal 1994
discusses the history of this topic, exploring such units and how humans developed the current state of logically recognizing and naming them.
See also
*
Available seat miles
*
Passenger load factor
*
List of countries by rail usage
References
External links
Scheduled Passengers Carried, World Air Transport Statistics 51st Edition, IATA
provides an example of transportation statistics
{{DEFAULTSORT:Transportation measurement
Economic data
Transport economics